The Victorian police (or any other functional police force) don't get to decide what's a "big deal" or not. That's the job of the Victorian parliament, that passes the laws. The cops' job, and their duty, is to enforce that legislation when a breach has been brought to their notice.
At the very least, it appears the act of animal cruelty we are discussing breaches the Wildlife Act (Victoria) 1975, in particular Section 58:
Wildlife Act 1975 - SECT 58
Molesting protected wildlife during close season
58. Molesting protected wildlife during close season
(1) Any person who-
(a) wilfully molests or injures protected wildlife or wilfully causes
protected wildlife to be molested or injured;
(b) wilfully disturbs, chases or herds protected wildlife or wilfully
causes protected wildlife to be disturbed, chased or herded;
(c) wilfully separates protected wildlife from its young or causes it to
be so separated-
shall be guilty of an offence against this Act. Penalty: 20 penalty units.
(2) Subsection (1) does not apply to any person acting in accordance with a
licence or authorisation issued under this Act.
The Bluetongue skink, like nearly all wild native fauna, is covered under the definition of "protected wildlife":
Wildlife Act 1975 - SECT 3
PART I PRELIMINARY
Definitions
3. Definitions
[...]
protected wildlife means all wildlife other than those kinds or taxon which-
(i) is a pest animal within the meaning of the
Catchment and Land Protection Act 1994; or
(ii) the Governor in Council from time to time by Order published in the
Government Gazette declares to be unprotected wildlife; or
(iii) are specified by Order of the Governor in Council published in the
Government Gazette pursuant to section 7A;
If the above is brought to the attention of the Sale police by a member of the public residing in the state of Victoria, they are obligated to investigate, and report back to the complainent within reasonable time. If they do not, then the matter can be raised with, for example, the Ombudsman's Office of Victoria, to determine why the Victorian police are not acting on a complaint.
I hope I'm making my point fairly clear by now. The most likely way to get an effective response to this is to have someone in Victoria make an official complaint to the Sale police, alerting them to the fact that there appears to be a fairly clearcut breach of the Wildlife Act 1975, and possibly other relevant laws, and there is ample evidence to enable the perpetrator(s) to be identified and police action to be taken.
Given that the perpetrators are minors, then an official police caution, or similar, might be the response. But even that's a result, particularly if the parents of the kids involved are possibly rudely woken up to what's been going on.